1. Field of the Invention
The present invention relates to the field of beneficiation of carbonate mineral substrates by removing undesired impurities. Specifically, the present invention relates to a method of beneficiation of carbonate ores using a combination of magnetic microparticles and a mineral-active compound containing a N or P functionality.
2. Description of the Related Art
Beneficiation is a term used in the mining industry to refer to various processes for purifying mineral substrates (such as mineral ores) to obtain value minerals. Beneficiation typically involves separating the desired or “value” minerals from other less desirable or “non-value” mineral(s) that may be present in the mineral substrate. In many cases, the degree of separation obtained strongly influences the quality of the beneficiated product. For example, value minerals such as calcium carbonate are used as pigments and fillers in a variety of end applications, e.g., coatings and fillers in paper, paint, plastic, ceramics, etc. In such applications, desirably higher levels of whiteness or brightness are typically associated with lower levels of impurities. However, carbonate minerals often contain a variety of discoloring minerals such as feldspar, orthoclase, chlorite, silica, anatase, micas such as muscovite and biotite, clays and iron phases. Also, minerals with relatively low impurity levels are often desired in other applications, such as in the electronics, optics and biomedical fields.
Some mineral separation processes involve the use of magnetic reagents and strong magnetic fields. PCT Publication WO 02/066168 discloses surface-functionalized magnetic particles that are said to be useful as magnetic reagents for mineral beneficiation. The magnetic particles are said to be at least comparable in size with the mineral particles, and thus it is apparent that the amount of material present on the surfaces of the magnetic particles is only a small part of the magnetic reagent. U.S. Pat. Nos. 4,834,898 and 4,906,382 disclose magnetizing reagents that are said to comprise water that contains particles of a magnetic material, each of which has a two layer surfactant coating including an inner layer and an outer layer. The inner and outer surfactant layers on the magnetic particles are said to be monomolecular and are different.
In prior magnetic separation processes it has been found that improved beneficiation has often been observed as the particle size of the magnetic microparticles is decreased. Thus, it has been desirable in certain applications, such as in kaolin beneficiation, to use magnetic microparticles with the smallest practical particle size